The explosive found in the packages, PETN, is the same as the material found in the December 2009 foiled underwear bomb attack in the United States. It's a highly explosive organic compound that belongs to the same chemical family as nitroglycerin. Six grams of PETN are enough to blow a hole in the fuselage of an aircraft.

Al-Asiri was also suspected in the earlier attempted bombing case, where a Nigerian man, Umar Farouk AbdulMutallab, is accused of trying to set off a bomb hidden in his underwear on a flight.

Al-Asiri's brother, Abdullah, also appeared on the Saudi Arabia's most wanted list. According to press accounts, it was Ibrahim al-Asiri who lured his brother to the jihadist movement.

In 2009, Abdullah al-Asiri died when he detonated a bomb on his body with the intent of assassinating Saudi Prince Muhammed Bin Naif, a top security official. The suicide bombing attempt failed to kill its target.

A few days after that attempt, the Watan newspaper in Saudi Arabia interviewed al-Asiri's mother and sisters.

Their mother described Ibrahim and Abdullah as regular teenagers growing up.

"They were not religious boys at the time. They used to listen to music and had a wide variety of friends, friends not like the ones they had later when they became more religious," she told Watan.

One of their sisters told the newspaper that the death of their brother Ali in a car accident in 2000 was a turning point in Ibrahim and Abdullah's attitude.

"It was after that that they started swapping video tapes and cassettes on the Mujahedeen in Chechnya and Afghanistan, and they became at times distant," the sister said. "Abdullah started to go out a lot with his new friends to camps known as 'preaching camps.'"

Ibrahim at one point was arrested in 2003 while trying with others to enter Iraq to wage jihad, his family told Watan. He was held in prison for nine months.

Also shortly after the attempt against the Saudi prince's life, the Saudi Gazette newspaper spoke with Ibrahim and Abdullah's father, who shed some more light on the young men's upbringing.

The family grew up in the Al-Jazira district of east Riyadh, he said, describing theirs as a pious family.

"We were living in Makkah two years ago and were planning to move back to Riyadh, but Abdullah and Ibrahim said they wanted to go to Medina before coming back with us," the father, Hassan, told the newspaper last year.

"Abdullah later contacted us to say he was out of the country, but didn't say where, and from that day on we had no more news of him until we saw his and his brother's pictures a few months ago in the media as on the list of wanted people."